An image recognition apparatus that recognizes white lines, preceding vehicles, oncoming vehicles, and the like using image data obtained by an on-board camera is known. In recent years, the performance of on-board cameras has improved. An on-board camera may output image data exceeding 8 bits. However, to reduce processing load on the image recognition apparatus, image data that exceeds 8 bits may be converted to 8-bit image data and then used for image recognition (refer to, for example, PTL 1).